By making [that] choice, then, I was shifting
my concentration from art-doing to art-experiencing;
an artwork would be done specifically for a gallery  in other
words, for a peopled space, for a space in which there were gallery-goers.
The gallery, then, could be thought of as a community meeting place,
a place where a community could be formed, where a community could
be called to order, called to a particular purpose.
Vito Acconci

As a reaction to the rigid, minimal sculpture
that immediately preceded it, it [installation art] displays much
of the same conceptual coolness and devaluation of relationships
at the same time that it opens up new possibilities of freedom from
the object and collaboration with the environment.
Max Kozloff

Websites related to installation:

Judy Chicago
This site showcases important installation works by feminist artist,
Judy Chicago. It includes the legendary installation, Womanhouse,
a large-scale collaborative project created by Judy Chicago and
Miriam Schapiro with students of the Feminist Art Program at Cal
Arts. Women transformed each room in the house to suggest the psychological
and social issues facing women in the 1970s. Other projects featured
on this site include: The Dinner Party, a symbolic history of women
in Western civilization; The Holocaust Project, an exploration of
one of the darkest periods in human history; and Resolutions, a
needlework project that reinterprets traditional sayings for postmodern
times.http://judychicago.com/

Christian Boltanski
Botanksi creates hauntingly beautiful, evocative installations out
of such materials as newspaper clippings, found photographs, clothing,
and candles. His work, often utilizing shadows and projections,
examines the transitory nature of peoples lives and communities.http://www.kemperart.org/exhibition.html